How well these 'standards' are supported on middle range hardware (pre GeforceFX) ? I know that a lot can be made with Cg there, while AFAIK opengl vertex/fragment program extension is just not supported at all. Please correct me if I'm wrong, but if it is true, I see a major counterargument to 'standard' shouting.

If we support the OpenGL shading language, is OpenGL 1.5 or OpenGL 2.0 required? I read the other thread, but don't know how to interpret it correctly. (OpenGL 1.5 does not support the shading language, but it's available as a set of extensions.)

I know that a lot can be made with Cg there, while AFAIK opengl vertex/fragment program extension is just not supported at all.

This is true, and I know only one vendor who supports GLSL (also sometimes named as GLslang) on their high-end cards - 3DLabs, and AFAIK GLSL is their development: http://www.3dlabs.com/support/developer/ogl2/index.htm. Currently this is approved as official ARB extension.

NVidia Cg can not be treated as vendor-specific language, at least because of it can generate code for ARB_vertex_program extension, supporrted by different vendors (say, 3DLabs and ATI). You can check FAQ at http://www.cgshaders.org/articles/interview_davidkirk02.php for more details. Cg is just one more layer on top of existing and supported OpenGL specs and extensions.

On the other hand, I read somewhere that NVidia has plans to support GLSL/GLslang.

Very important point is that for a moment I am not sure if there are bindings for GLSL extensions in JOGL (or other OpenGL bindings for Java), while functional Cg bindings are existing and tested. They include nice mechanisms for specifying parameters for high-level Cg programs, so it is much easier to integrate than other shading languages.

If we support the OpenGL shading language, is OpenGL 1.5 or OpenGL 2.0 required?

I don't think you should loose compatibility with OpenGL 1.2, so if application does not use programmable shaders it should run no pbs on the older HW. Actually, app should (can) detect if these functions supported on the system before using them.

I wanted to know which OpenGL version is required to use the shading language if we support it.

Actually, this does not depend on OpenGL version but rather on availability of specific extensions:

You can start using Cg with OpenGL 1.3 if you have available extensions like NV_vertex_program, NV_vertex_program1_1 or ARB_vertex_program.

App should not rely on OpenGL version but only on presence of extension and/or function entry points, because of some vendors may decide to drop some older extensions, besides of they are part of OpenGL spec.

Unfortunately I just read in a press release from October about their contribution to the OpenGL shading language: http://www.nvidia.com/object/IO_9075.html"[..] NVIDIA was also one of the primary contributors to the new OpenGL® Shading Language extension. [..]"

Maybe I confused their contribution with "already supported by current drivers"... ? :-(

This is exacly what I meant - AFAIK, NVidia does not support GLslang yet. They have plans to add this, but for a moment they do not support it, so even if we'll add GLslang to Xith3D right now this will be useless for majority of devs, especially on non-Windows platforms, while Cg will work at least on Windows & Linux.

Cg is also mostly useless for users of non nVidia hardware. While I can go through the hassle of building a shader and compiling it with nvidias tools into something that can run on ATI hardware, if I do that - not really a whole lot of sense supporting Cg at all - as I'm just making an OpenGL call to render with the compiled shader.

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